The organization and mechanism of coordinate expression of the ribosomal protein genes in Saccharomyces cerevisiae will be investigated, utilizing recombinant DNA molecules that contain five different ribosomal protein genes. Long stretches of DNA contiguous to these cloned genes will be isolated by screening a library of large fragments of yeast DNA cloned in bacteriophage lambda. These DNA's will be assayed for the presence of other ribosomal protein genes to determine whether ribosomal protein genes are clustered to any significant extent in the yeast genome, and will be used as probes to determine whether any of the genes adjacent to yeast ribosomal protein genes are subject to the same coordinate control. Comparative sequence analysis of DNA flanking both ends of the three cloned, coordinately expressed genes versus the two cloned functionally related, but not coordinately controlled, ribosomal protein genes will provide a unique opportunity to ascertain which sequence elements are involved in coordinate gene expression. A putative ribosomal protein gene with an assayable function, the cryptopleurine resistance gene, will be isolated by overlap hybridization with cloned sequences from the nearby MAT locus. The cycloheximide resistance gene will be purified by transformation of cycloheximide sensitive yeast to cycloheximide resistance, using a bank of yeast DNA cloned in a yeast transformation vector. Controlling sequences adjacent to these genes will be mutagenized in vitro, and loss of function will be assayed by reintroduction of these sequences into yeast by transformation, in order to assay for those sequences necessary for expression of these genes.